Anemia characterized by a lack of vitamin b12 is called
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Anemia Characterized by a Lack of Vitamin B12: Pernicious Anemia
Introduction to Pernicious Anemia
Pernicious anemia is a specific type of anemia caused by a deficiency in vitamin B12, also known as cobalamin. This condition arises primarily due to the body's inability to absorb vitamin B12 from the gastrointestinal tract, often because of the absence of intrinsic factor, a protein necessary for vitamin B12 absorption 25.
Pathophysiology and Causes
Autoimmune Gastritis and Intrinsic Factor Deficiency
The most common cause of pernicious anemia is autoimmune gastritis, which leads to the destruction of stomach cells that produce intrinsic factor. Without intrinsic factor, vitamin B12 cannot be absorbed, leading to a deficiency 56. This autoimmune condition is often associated with other autoimmune disorders, such as type 1 diabetes and thyroid diseases .
Dietary Deficiency and Malabsorption
While less common, dietary deficiency and malabsorption due to gastrointestinal surgeries or chronic conditions can also lead to vitamin B12 deficiency. Chronic alcohol use and certain medications can impair vitamin B12 absorption, contributing to the development of pernicious anemia 39.
Clinical Presentation and Diagnosis
Symptoms and Hematological Findings
Patients with pernicious anemia often present with symptoms of anemia, such as fatigue, weakness, and pallor. Neurological symptoms, including paresthesia, loss of proprioception, and cognitive disturbances, are also common due to the role of vitamin B12 in nerve function 46. Hematologically, pernicious anemia is characterized by macrocytic anemia, with elevated mean corpuscular volume (MCV) and low hemoglobin levels .
Diagnostic Challenges
Diagnosing pernicious anemia can be challenging due to its insidious onset and the variability of symptoms. Laboratory tests typically show low serum vitamin B12 levels, elevated methylmalonic acid (MMA), and homocysteine levels. The presence of gastric parietal cell antibodies (GPCA) can help confirm the diagnosis 56.
Complications and Misdiagnoses
Hemolytic Anemia and Pseudo-Thrombotic Microangiopathy
Severe vitamin B12 deficiency can lead to hemolytic anemia and thrombocytopenia, conditions that may be misdiagnosed as thrombotic microangiopathy (TMA) or thrombotic thrombocytopenic purpura (TTP). This misdiagnosis can result in unnecessary and costly treatments like plasmapheresis, which are ineffective for vitamin B12 deficiency 178.
Non-Immune Hemolytic Anemia
In rare cases, vitamin B12 deficiency can cause non-immune intramedullary hemolysis, a condition where red blood cells are destroyed within the bone marrow. This form of hemolytic anemia is often associated with chronic alcohol use and requires prompt vitamin B12 supplementation for treatment 39.
Treatment and Management
Vitamin B12 Supplementation
The primary treatment for pernicious anemia is vitamin B12 supplementation, typically administered via intramuscular injections. Initial treatment involves daily injections for a week, followed by weekly injections for a month, and then monthly maintenance doses 36. This regimen effectively corrects the deficiency and alleviates both hematological and neurological symptoms.
Monitoring and Follow-Up
Regular monitoring of vitamin B12 levels, hemoglobin, and neurological function is essential to ensure effective management and prevent recurrence. Patients with pernicious anemia often require lifelong supplementation and periodic evaluations to monitor for potential complications 46.
Conclusion
Pernicious anemia, characterized by a lack of vitamin B12, is primarily caused by autoimmune gastritis leading to intrinsic factor deficiency. It presents with a range of hematological and neurological symptoms and can be complicated by conditions like hemolytic anemia. Accurate diagnosis and prompt treatment with vitamin B12 supplementation are crucial for effective management and prevention of long-term complications. Regular monitoring and follow-up are essential to ensure sustained health and well-being in affected individuals.
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Do all the patients with vitamin B12 deficiency have pernicious anemia?
Only 18.9% of patients with vitamin B12 deficiency are diagnosed with pernicious anemia by the WHO definition.
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